What problem will a 90ecu in a 91-94 car cause?

[smokehouse_83]

I recently pulled the ECU in my 92 talon TSI to find out if it was eprom or not and it must be out of a junk yard or something cause it has 90 talon 4x4 wrote all over it. There is no wires switched on the ecu wiring harness, but it does have the little tach interface by the coil which I though was a 90 option? It also has a black top cam sensor. The car seems to run fine with the ecu except when I rev it over 4 grand or so it starts to miss, but if I shut the car down and let it sit for awhile I can start it and it runs fine again. Does anyone know what problems a 90 ecu in a 91+ car will cause? I pluged in the ecu from my old 91 and the miss seemed to go away, but the car dies cause the caps are shit in that ecu.

 

[dsm-onster]

I THINK that there have only been problems with putting a 1992-1994 ecu into a 1990-1991 car... Then other way around has not been a problem... I have a 1990 with a 1993 ecu and i had to change some things to get my tach to work right BUT there has never been a problem like yours reported from my research or memory. I'd lok elseware to solve the upper rpm miss. Do you have a logger?

 

[smokehouse_83]

I have a logger, but need to find a power source for my laptop (lost the old one). The tach works fine. I put the snap on scanner on it (I am a mechanic), but you cant see as much info as you can with the logger. Everything I can see looks ok though, no codes or anything. You think if the airflow & the throttle sensor wires were different on the ecu you would get an airflow code or it wouldnt start? I am going to put it on the ignition scope and check it out to see if its a spark problem.